1. Field of the Invention
The present invention is related to measuring the stability of a radar system and, more particularly, measurement of stability of a radar system without interrupting operation of the system and including instability caused by timing jitter in addition to other causes of instability.
2. Description of the Related Art
Instability in a radar transmitter can severely degrade the ability of Doppler filter(s) in a radar receiver to suppress clutter echoes However, instability such as small fluctuations in amplitude or phase from pulse to pulse is difficult to detect and isolate. Furthermore, although good stability is a requirement of modern radar, the measurement of stability has required special test procedures which are incompatible with normal operation of the radar.
In addition, the trend in radar is toward unmanned operation to reduce the cost of operation. Most critical performance parameters, with the exception of stability, can be measured by remote control testing without disruption of normal operation. Fault isolation tests can be conducted to determine which replaceable parts should be brought to the site by maintenance personnel, thereby reducing the cost of maintenance. However, virtually all methods of measuring stability are extremely difficult to apply from a remote location due to the calibration and visual interpretation of standard test equipment which is usually performed by an operator at the site of the radar antenna. Such visual interpretation typically includes eyeball integration of a fluctuating display, such as that provided by a spectrum analyzer Furthermore, known methods of measuring stability ignore instability caused by timing jitter which can be a significant source of instability.
For the above reasons, stability is often only measured when a radar system has been shut down because it has degraded to such an extent that clutter alarms are grossly excessive. In other words, it is difficult to schedule maintenance at a time of low usage of a radar system to improve degradation of stability, due to the difficulty in identifying the extent of degradation of stability.